Study On Influence Of Y-chromosome Microdeletions And The Genetic Characteristic On Male Infetrility

According to the World Health Organization, approximately10–15%of thereproductive-aged population are infertile in the world. Male-specific factors havebeen implicated in approximately half of these cases. So people are paying more andmore attention on male infertility. The reasons lead to male infertility are complex,such as genetic, infectious, endocrine and so on. The recent researches showed thatgenetic factor was still the main reason result in the male spermatogenic failure, dueto genetic factors are susceptible to external environmental factors, the mechanism ofgenetic factors leading to male spermatogenic failure is more complex. It has beendemonstrated that Y-chromosome microdeletions and chromosomal anomalies wereimportant genetic factors leading to male infertility, but researches about thecorrelation between them were varying.In1976, Tiepolo speculated that the long arm of Y chromosome exists geneswhich control spermatogenesis, and named it azoospermia factor(AZF) region, and itis divided into3subregions (AZFa, AZFb, AZFc). In male infertility field, theY-chromosome microdeletions of the three subregions are specific to AZFmicrodeletions. AZFc deletion frequency was the highest, and clinical manifestationswere diversity--from azoospermia to the sperm count is normal, but with abnormalsperm morphology, it has become a difficult and hot spot both domestic and overseas.The type of AZFc deletion includes completed and AZFc partial deletion of the AZFcregion. Although it has been proven that there have some relationships between AZFmicrodeletion, AZFc partial deletion and male infertility, but there were differentreports about the deletion type and the phenotype between different races, adding theexternal environmental factor, so the mechanism needs further study. Therefore, wewant to state whether the regional differences exist in Changchun area or not throughthe research on the type and phenotype of AZF microdeletions and AZFc partialdeletions of male infertile patients in this region. Research showed that serum reproductive hormone analysis was helpful to thediagnosis of male infertility, we all know that patients with AZF microdeletions oftenhave multiple changes of hormone levels, but the relationship between them is unclear,we should discuss which index change is better to reflect its relevance, and moresignificant in the diagnosis of male infertility.Accumulating evidence has suggested that genetic defects of AZF microdeletionsactually facilitate the transmission of Y-chromosome microdeletions frominsufficiently fertile fathers to their male offspring, AZFc partial deletions throughassisted reproductive technology as well. Therefore, we suggest that patients shouldundergo pre-implantation genetic diagnosis before assisted reproduction try to choosefemale offspring, so as to cut off the genetic pathway to reduce the verticaltransmission risk. However, there have no report about the transmitted from fathers toinfertile son via natural transmission, and explore the type and clinical phenotype ofthe AZF microdeletions and (or) AZFc partial deletion in the two generations. Wehope to provide a theoretical basis for the diagnosis and genetic counseling of infertilemales. There are five objectives in our study.1. To investigate the frequency and types of AZF microdeletions in infertilemales of our region.2. To study the correlations between AZF microdeletions and the reproductiverelevant hormone levels.3. To discuss the correlations between AZF microdeletions and chromosomalanomalies.4. To evaluate whether exsit new type of AZFc partial deletions in infertile malesof our region, and the correlations between the type of AZFc partial deletions andmale infertility.5. To discuss the correlation between AZF microdeletions, AZFc partial deletions,reproductive relevant hormonal levels and vertical genetic risk on father-son pairsover natural vertical transmission.MethodsWe evaluated1416male patients aged22–44years had detected Y-chromosomemicrodeletions attended the outpatient infertile clinic of clinical hospitals ofChangchun, between August2009and December2011.60fertile males aged24–37years were used as controls. Semen examinations were evaluated the subjects semen quality. Peripheral blood samples of the subjects were taken to examine geneticcharacteristic using karyotype analysis and PCR technology, Electrochemiluminescenceimmunoassay was used to analyze reproductive hormone levels and enzyme-linkedimmunosorbent assay was used to analyze inhibin B levels.Results1. One hundred and twenty-two of1416patients (8.62%) had AZFmicrodeletions. Among the deletion patients, the most frequent microdeletions wereAZFc(6.78%), followed by AZFb+c(1.20%),AZFb (0.42%), and AZFa(0.07%).The frequency of microdeletions among severely oligozoospermic(17.65%) washigher than those among azoospermic males(10.58%).2. Among the deletion patients, deletions in sY254and sY255(92.62%)were themost common in our study, followed by sY152(87.70%), sY157(69.67%), sY134(17.21%), sY127(16.39%), sY143(10.66%), sY84(2.46%)and sY86(2.46%).3. There were multiple segmental deletions(11/122) in our samples amongazoospermic patients with Y-chromosome microdeletions, all of them had deletions inthe AZFb+c regions and existing sites were in the AZFb region. The most region ofAZF deletions was AZFc with sY152, sY254, sY255, sY157deletions.4. Of AZF microdeletions patients, between azoospermic group and fertile group,the difference of FSH level was statistically significant (P<0.05), and the differencesof LH, T and INHB(20-29years) levels were significant statisticalsignificance(P<0.01). Between severe oligozoospermic group and fertile group, thedifferences of T, INHB (20-29years) and INHB(30-44years) levels were significantstatistical significance(P<0.01). Between oligozoospermic group and fertile group, thedifferences of LH, T and INHB(20-29years) levels were significant statisticalsignificance(P<0.01). There were no differences in other groups compared with fertilegroup (P>0.05).5. Six of the azoospermic patients with microdeletions had chromosomalanomalies. From the chromosomal karyotype point, four of these patients werechromosomal mosaics. From the deletion region point, four of them were multiplesegmental deletions in the AZFb+c regions.6. In this study, there were four types of AZFc partial deletions in infertile group,including gr/gr deletions (6.37%,78/1224), b2/b3deletions(10.05%,123/1224), b1/b3deletions(0.41%,5/1224), and the novel partial b1/b2deletion was identifiedby the absence of sY142, sY1258, sY1161, sY1197deletions(0.08%,1/1224). Therewere two types of AZFc partial deletions in fertile group, including gr/gr deletions(6.67%,4/60) and b2/b3deletions(3.33%,2/60). Of infertile group, betweenoligozoospermic group and fertile group, between normal sperm group and fertilegroup, the differences of partial AZFc b2/b3deletions frequency were statisticallysignificant (P<0.05). There were no differences in other groups compared with fertilegroup (P>0.05).7. AZF and AZFc partial deletions analysis detections were performed on tenfather-son sample pairs. De novo microdeletions in AZF regions were found to havearisen through natural transmission in three father-son pairs, Expanded microdeletionsin the AZFc region were identified in the other seven father-son pairs. There was aspecial father-son sample pair which father had (sY152, sY254, sY255)+(sY1191)deletions, while the son had sY157in the AZFc region and sY1291, sY1054,sY1206in the AZFc partial deletions expanded by natural transmission.8. Of ten father-son sample pairs, between father group and son group, thedifferences of FSH, T and INHB(20-29years) levels were significant statisticalsignificance(P<0.01). There were no differences in other groups compared with fertilegroup (P>0.05).Conclusions1. Our sample showed a higher frequency of AZF microdeletions among severelyoligozoospermic than those among azoospermic males, AZF microdeletions mostcommonly in the AZFc region. Severely oligozoospermic and oligozoospermic malesonly have AZFc region deletion. So the frequency of AZF microdeletions sites andregions could have some association with area of male.2. AZF microdeletions could result in the change of FSH, LH, T and INHB levels,The lower level of inhibin B and T of unknown cause infertile male may be usefulfeatures for AZF microdeletions.3. The result pointed out the genes located in the AZFb and AZFc regions, notonly be related to spermatogenesis, but also the stability of the Y chromosome. AZFmicrodeletions and chromosome mosaicism may further reduce sperm qualitytogether.4. In our samples, Y-chromosome AZFc partial deletions could have some association with area of male, partial AZFc b2/b3deletions could have certainassociation with infertility, partial AZFc gr/gr deletions could have no associationwith infertility, and the deletions may not be the risk factors which affectspermatogenesis.5. Y-chromosome microdeletions were passed from a father to a son via naturaltransmission and found that the microdeletions may be expanded during suchtransmission or arise de novo, in which the sons carrying them may have beenexposed to environmental mutagenic sources or experienced sporadic geneticprocesses. The differences of the reproductive hormone levels between sons andfathers prompt the trend of severity on the clinical phenotype of offspring contrast totheir fathers, and ultimately cause infertility.